Brush and mounting therefor



Nov. 24, 1931. c. L. KENNEDY BRUSH AND MOUNTING THEREFOR Filed Dec. 28. 1929 /6 I fnienfor mine!!! .tact resistances may Patented Nov. 24, 1931 UNITED sryrss PATENT OFFICE oAnLToN I rKENNEDY, or BRAINTREE MAS SA CfiUSE TTS, AssI Non ro THE 110132211 CABOT ELECTRIC COMPANY, OF ROXBURY, MASSACHUSETTS, A CORPORATION or MASSACHUSETTS BRUSH AND MOUNTING THEREFOR Application filed December 28 1929. SeriaINo. 417,197.

The present invention relates to brushes and mountings therefor and more particularly to short-circuiting brushes for repulsion motors.

In the ordinary repulsion or repulsioninduction motor, the commutator is short-circuited at two or more points by one or more pairs of brushes. in a separate brush-holder and sincethe brushes are not of great thickness, there is a tendency for them to chatter in their supports. This chattering not only causes noise but also prevents proper commutation. Moreover, inasmuch as themotors are usually wound so that the generated voltage is low, special precautions must be taken to connect the brushes together with a minimun of electrical resistance, in order that the connot unduly limit the short-circuit current. i 4

The object of the present invention is to provide a brush anda mounting therefor whereby any tendency to chatter is entirely eliminated and also complete short-circuiting between the proper pointsof the commutatoris effected. I

With this object inview, the principal feature of the invention comprises a, single brush member constructed to take the place of apair of brushes in the usual motor and being of yoke or U-shape, having spaced legsadapted to engage the commutator, which legs are rigidly connected together by a cross-piece of low electrical resistance. In its preferred form, the invention comprises a sin gle integral yoke-shaped piece of carbon or other conducting material having good commutating' properties and so formed that the 40 -legs are directly short-circuited without the use of electrical connections which might introduce contact resistances. Because this brush subtends a comparatively large arc of the commutator, all tendency to chattering is eliminated.

. the commutator.

Other features of the invention consist in Each brush is mounted certain novel features of construction, combmations, and arrangement, of parts hereinafter described and claimed. g

In the accompanying drawings, Fig. 1 is a sectional elevation of a repulsion motor embodying the brush and brush supportof,

the present invention, being a sectionon line 1-1 of Fig. 2; Fig; 2 is an end view of the motor with the end bonnet removed Fig, Sis a plan view of the brush assembly; Fig. 4 is an end view of the assembly shown in Fig.3; and Fig.- 5 is a side elevation of the brush assembly. i i

The invention is herein illustrated and described as embodied in afour pole repul sion motor having provision for brush contacts with the commutator at intervals of 90. The motor isv illustrated as employ by brushes 12. Each brush, as shown in detail in'Fig. 4;, is of yoke or U-shapehaving two legs 14 adapted for direct engage ment with the commutator, the legs being connected by an integral arch 16, subtending'the entire angle between the legs The entire brush, which takes the place of a'pair g of brushes in the usual motor, is formed of a single integral piece of carbon or other good commutating material. Inthe four pole motor shown in Fig. 2, the brush legs subtend an angle of 90. v A

The brush is mounted in a support 18 of particularly simple construction, being formed from a single piece of sheet metal.-

As shown in Fig. 3, the support has an end face 20, sides 22, and feet 24. A channel for the brush is formed by inwardly extending projections 26 and 28 struck out from the material of the sides 22. The channel is of such form as to permit free movements of the brush toward or away from thecom mutator but to restrain it against movement in other directions. A pair of indentations 28 are formed in the ends of the channel to serve as positioning means for the brush. A spring fulcrum 30 is struck up from each side face 22 and turned inwardly. Aspring 34 serves to press the brush toward the commutator. The spring is of wire having feet 36 symmetrically pressing on the outer surface of the arch 16 of the brush at points disposed somewhat inwardly from the legs 14. The spring is formed with coils 38 which are received on the fulcrums 30 and the ends of the springs are turned over the side faces of the support, as indicated at 4:0.

The feet 24 of the support are attached to an annular mounting plate 42 by a suitable means, preferably by spot welding. As shown in Fig. 1, the plate 42 in the form of a ring is received in an annular groove formed in the end bonnet 0f the motor. The position of the brushes may be varied by rotating the ring to any desired position. The ring is clamped in adjusted position by a bolt 48 passing through the end bonnet and screwing into a clamping nut 44 which engages the ring 412. The position of the ring is indicated by a pointer 46. Access to the ring for purpose of adjustment may be gained by removing the cover plate 48.

In the event that only a single brush assembly is employed, may be the case in motors of the repulsion type, a mounting plate in the form of a complete ring is not necessary. The plate may then be cut in the shapeof a sector, as indicated by the dotted lines 49 of the Fig. 4.

If the motor to run as an induction rotor. after being brought up to speed as a repulsion motor, any suitable means may be provided. for completely short-circuiting the commutator segments.

The advantages of the present invention are that the yoke-shaped brush which sub-- tends a considerable arc of the commutator entirely eliminates any tendency to chatter,

thus conducing to quiet operation and proper commutation. Also the electrical opera-- tion is improved because of the low resistauce between short-circuited points of the commutatonthere being no contact resistances except those interposed between the commutator and the brushes themselves. The construction is exceedingly simple in that only a single stamping and a single springare necessary to form the complete brushrholder.

the commutator, a mounting for the brush comprising a member having a channel in which the brush is received and adapted to permit movements of the brush as a whole toward and away from the commutator of the motor, and a spring engaging with the brush to press it toward the commutator.

3. The combination with a commutator, of a brush assembly comprising a rigid brush having spaced legs to separately engage "the commutator and to span the polar are thereof, a mounting for the brush comprising a single piece of sheet metal formed to provide a channel for the brush and having spring supporting projections, and a spring mounted on the. projections and having portions symmetrically engaging, the brush.

l. A brush assembly for a motor having, in combination, a rigid yoke-shaped brush member having spaced legs and a connecting arch, a brush mounting compr sing an end face and side faces, projections turned inwardly from the side faces to, form with the end face a channel to receive the brush 1Il6111l761,-21I1l-21 spring supported on the brush mounting and having portions engaging the arch of the brush member.

5. In a repulsionmotor having a frame, a rotor and a commutator, a brush assembly having, in combination, rigid yoke-shaped brush member having spaced legs and a connecting arch, a brush mounting comprising a single piece of sheet metal formed with an end face and side faces, projections turned inwardly from the side faces to form with the end face a channel to receive the brush member, spring supporting projections turned inwardly from the side faces, a spring having coils supported by the projections and provided with feet engaging the arch of the brush member to press the brush toward the commutator, a plate to which the brush mounting is secured, and means for adjustably supporting the plate in the motor frame. y

6. The combination with a motor having a commutator, of a brush comprising a single integral yoke having legs to subtend the polar arc of the commutator and an arch connecting the legs.

In testimony whereof I have signed my name to this specification.

CARLTON L. KENNEDY. 

